Design Interface And Modulate The Transport Properties Of Two-dimensional Heterjunctions: A Theoretical Study

Since the discovery of graphene,more and more two dimensional materials have been discovered and prepared.Mo Se₂ is one member of the transition metal dichalcogenides.Unlike graphene,Mo Se₂ have a suitable band gap,which have a great potential for making electric devices.Unfortunately,the Schottky barrier formed by contacting with electrodes limits the further improvement of Mo Se₂.In this paper,first principles calculations are carried out to study the effect of contact configurations,doping and electrode materials.At first,we have investigate the effect of contact configurations on the intrinsic electronic and transport properties of borophane-Mo Se₂ heterojunction.Calculations show that metallic behavior is appeared in semiconductor Mo Se₂ as a result of contact with borophane.And the calculated band alignments indicate that n-type Ohmic contacts are formed between borophane and Mo Se₂.But the band alignments are different between different configurations.Also the contact configurations are important for the electronic transport properties of borophane-Mo Se₂ heterojunction.Then,we investigated the Schottky barrier and transport property of borophane-Mo Se₂ vd W heterostructure with Li,Na and K doping.The results demonstrate that the doping can induce more charge transfer,making the p-type Schottky contacts become n-type Ohmic contacts.However,all of these doping forms decrease the transmission coefficient and current due to the increase of interlayer distance.Later,the electronic and transport properties of Nb S₂-Mo Se₂ and Ta S₂-Mo Se₂heterostructures have been studied.Four different contact configurations between Nb S₂?Ta S₂?and Mo Se₂ are constructed and investigated.Calculations show that metallic behavior is appeared in semiconductor Mo Se₂ as a result of contact.Due to the strong interaction,the edge induced band gap states can be generated.The results of band alignments indicate that good p-type Ohmic contacts are formed between Nb S₂ and Mo Se₂,while p-type Schottky contacts are formed between Ta S₂ and Mo Se₂.And the currents are quite different in different configurations.For all the represented configurations,the edge induced transmission channels enhance the current at low bias,then the negative differential resistance phenomena appears.At last,we have investigate electronic properties of heterojunction combined by the van der Waals interaction with different materials.The Schottky barrier of different heterojunction shows different behavior.A good Ohmic contacts are formed when Nb S₂,Ta S₂ and VS₂ are used for electrodes and Mo Se₂ center,while the Schottky contacts are formed when Nb Se₂,Ta Se₂ and VSe₂ are used for electrodes.For all the systems,the tunneling barriers are quite different,which play an important character for performance of contact resistance.